Panel Geometry Research Articles

Role of Dynamic Response in Inclined Transverse Crack Inspection for 3D-Printed Polymeric Beam with Metal Stiffener.

This paper aims to quantify the relationship between the dynamic response of 3D-printed polymeric beams with metal stiffeners and the severity of inclined transverse cracks under mechanical loading. Very few studies in the literature have focused on defects starting from bolt holes in light-weighted panels and considered the defect's orientation in an analysis. The research outcomes can be applied to vibration-based structure health monitoring (SHM). In this study, an acrylonitrile butadiene styrene (ABS) beam was manufactured through material extrusion and bolted to an aluminium 2014-T615 stiffener as the specimen. It simulated a typical aircraft stiffened panel geometry. The specimen had seeded and propagated inclined transverse cracks of different depths (1/1.4 mm) and orientations (0°/30°/45°). Then, their dynamic response was investigated numerically and experimentally. The fundamental frequencies were measured with an experimental modal analysis. The numerical simulation provided the modal strain energy damage index (MSE-DI) to quantify and localise the defects. Experimental results showed that the 45° cracked specimen presented the lowest fundamental frequency with a decreased magnitude drop rate during crack propagation. However, the 0° cracked specimen generated a more significant frequency drop rate with an increased crack depth ratio. On the other hand, several peaks were presented at various locations where no defect was present in the MSE-DI plots. This suggests that the MSE-DI approach for assessing damage is unsuitable for detecting cracks beneath stiffening elements due to the restriction of the unique mode shape at the crack's location.

Impact of Discrete Fracture Characteristics on Longwall Top Coal Stability

Discrete fractures may exist in thick coal seam and significantly impact the top coal stability in the Longwall Top Coal Caving method (LTCC) both ahead of shield support (top coal fall) and behind shield support (top coal caving). The top coal stability in such conditions is not well understood in the literature and has been studied from either fall or caving behaviour. In this paper, a discontinuum-based numerical program is used to study longwall top coal stability when discrete fractures exist in coal seam and vary in characteristics (i.e., orientation, density, stiffness, strength, and intersecting fractures). The study demonstrates that the existence of discrete fractures decreases the top coal stability ahead of shield support, particularly in initial face extraction. The parametric study finds that when the fracture orientation makes an angle of 90 degrees to the positive x-axis, it has the least impact on top coal fall. When the fractures plunge into the mined-out area, they facilitate top coal caving and vice versa when they plunge into the unmined area. The study reveals that the fracture density is directly proportional to top coal fall and top coal caving. Meanwhile, the fracture stiffness and strength are inversely proportional to both top coal fall and caving. The study also demonstrates the important role of coal seam characteristics (strength, elastic modulus, and depth) in top coal fall. The findings from this paper can assist engineers in improving panel geometry design and roof control for efficient underground mining when discrete fractures exist and vary in a coal seam.

Application of point interpolation mesh-free method for magneto/electro rheological vibrations of sandwich conical panels

Magneto-rheological or electro-rheological materials, due to many possible control-based applications have acquired lots of attention. So, in the present work, as the first attempt, a point interpolation method is exploited to evaluate vibrations of the sandwich conical panel with magneto-rheological or electro-rheological core, and composite face sheets. Through the linear viscoelastic hypothesis, and in the pre/post-yield zones, the correlation of shear stress-strain for magneto-rheological fluid is applied. The equilibrium equations are governed by the principle of Hamilton in addition to the first-shear deformation (FSD) hypothesis. By satisfying the compatibility equations, the interfaces of the core along with composite face layers are simulated. Upon polynomial basic function, shape functions together with the approximate form of the displacement field are constructed. The correctness of the computational approach is certified through the analogical investigation. The results show that number of face layers, thickness, the pattern of composite layers, weight fraction, and electric/magnetic field, together with the geometry of the conical panel have an imperative impact on the system's natural frequency in addition to the loss factor index.

Tetramine Aspect Ratio and Flexibility Determine Framework Symmetry for Zn8 L6 Self-Assembled Structures.

We derive design principles for the assembly of rectangular tetramines into Zn8 L6 pseudo-cubic coordination cages. Because of the rectangular, as opposed to square, geometry of the ligand panels, and the possibility of either Δ or Λ handedness of each metal center at the eight corners of the pseudo-cube, many different cage diastereomers are possible. Each of the six tetra-aniline subcomponents investigated in this work assembled with zinc(II) and 2-formylpyridine in acetonitrile into a single Zn8 L6 pseudo-cube diastereomer, however. Each product corresponded to one of four diastereomeric configurations, with T, Th , S6 or D3 symmetry. The preferred diastereomer for a given tetra-aniline subcomponent was shown to be dependent on its aspect ratio and conformational flexibility. Analysis of computationally modeled individual faces or whole pseudo-cubes provided insight as to why the observed diastereomers were favored.

Tetramine Aspect Ratio and Flexibility Determine Framework Symmetry for Zn8L6Self‐Assembled Structures

AbstractWe derive design principles for the assembly of rectangular tetramines into Zn8L6pseudo‐cubic coordination cages. Because of the rectangular, as opposed to square, geometry of the ligand panels, and the possibility of either Δ or Λ handedness of each metal center at the eight corners of the pseudo‐cube, many different cage diastereomers are possible. Each of the six tetra‐aniline subcomponents investigated in this work assembled with zinc(II) and 2‐formylpyridine in acetonitrile into a single Zn8L6pseudo‐cube diastereomer, however. Each product corresponded to one of four diastereomeric configurations, withT,Th,S6orD3symmetry. The preferred diastereomer for a given tetra‐aniline subcomponent was shown to be dependent on its aspect ratio and conformational flexibility. Analysis of computationally modeled individual faces or whole pseudo‐cubes provided insight as to why the observed diastereomers were favored.

Quantitative Identification Method for Glass Panel Defects Using Microwave Detection Based on the CSAPSO-BP Neural Network.

To address the problem of the quantitative identification of glass panel surface defects, a new method combining the chaotic simulated annealing particle swarm algorithm (CSAPSO) and the BP neural network is proposed for the quantitative evaluation of microwave detection signals of glass panel defects. First, the parameters of the particle swarm optimization (PSO) algorithm are dynamically assigned using chaos theory to improve the global search capability of the PSO. Then, the CSAPSO-BP neural network model is constructed, and the return loss and phase of the microwave detection echo signal of glass panel defects are extracted as the input feature quantity of the network, from which the intrinsic connection between input and output is found through network training and testing to achieve the prediction of the depth and width of glass panel surface defects. The results show that the CSAPSO-BP network model can more accurately characterize the defect geometry of glass panels than the PSO-BP network model.

Computational study on the panel size effects of the compressive load-bearing capacity after impact of laminated composites

Computational results on the panel size effect in the compression after impact (CAI) deformation and damage are presented in this paper. The experimental counterpart of this paper is Lin et al. (2022). The in-plane sizes studied are 152.4 mm × 101.6 mm, 177.8 mm × 177.8 mm, and 330.2 mm × 330.2 mm. The thicknesses studied are 24-ply (3.1 mm) and 48-ply (6.2 mm). The two stacking sequences are [45/-45/0/90/0/0]ns and [45/0/-45/90]ns. The material system studied is IM7/977-3. Enhanced Schapery Theory with 2D plane stress states (2D EST) have been used for the progressive failure analyses. Predicted LVI-induced damage was transferred onto the CAI mesh based on a damage transferring algorithm. The results show that 2D EST can successfully capture the deformation and CAI-induced damage patterns of the panels with various sizes. With detailed computational results, different mechanisms for the CAI failure have been analyzed and categorized. A more rigorous and practical term — compressive load-bearing capacity after impact (CLBCAI) has been proposed to replace compressive strength after impact (CSAI) to account for the effects of impact damage and panel geometry. This paper provides results to show that the existing industrial standard D7137 (2017) is limited and may need to be replaced.

Experimental vs. Numerical Computation of Acoustic Analyses on the Thickness Influence of the Multilayer Panel

Sound-absorbing panels made with a perforated front and a sound-absorbing material on the back have been used in many forms of construction for a long time. It is a reasonably efficient system, obtaining high values of sound absorption at a specific resonant frequency, depending on the design of the structure of the sound-absorbing multilayer panel. The present work considers an acoustic panel in two constructive types, consisting of four layers: a front panel made of perforated sheet, polyethylene foam foil, basalt wool board with two different thicknesses, and a back panel of the non-perforated sheet. Due to the different thicknesses of the basalt wool board, for the multilayer structure of the acoustic panel, differences in acoustic impedance and acoustic absorption can be highlighted, experimentally determined with an impedance tube, using the transfer function method (TFM) based on EN ISO 10534-2 in the frequency range 100–3200 Hz. In the meantime, a method was developed to predict the sound absorption coefficient, namely the prediction of sound absorption coefficient using the transfer matrix method (PSAC-TMM). This computational model of the multilayer acoustic panel is introduced considering the internal geometry of the multilayer panel, as well as the computation of the acoustic impedance of each layer, all gathered through the transfer matrix method (TMM). Comparative analyses between experimental data and predictive results using PSAC-TMM were performed, validating the PSAC-TMM as a predictive method to estimate the sound absorption coefficient for acoustic multilayer panels.

Panel Destressing Strategies for Remnant Pillar Extraction

Large-scale panel destressing is a rockburst mitigation technique employed in deep hard rock mines during remnant pillar extraction. Panels are choke blasted in the pillar footwall to cutoff the far-field major stress in the mining area and deviate them around the pillar. In this study, the effects of panel geometry and far-field stress magnitude are investigated. Destress blast performance is assessed by measuring change to the energy release rate (ERR) of all mining steps during the extraction of a simplified remnant pillar due to destressing. It is demonstrated that the energy release rate (ERR) of critical stopes is reduced by 30% with the base panel geometry. The panel thickness is shown to have the most influence on the efficiency of destressing, followed by the stand-off distance between the panel and the pillar and the overhang length of the panel. The effect of far-field stress magnitude on the ERR is also investigated, and the destress blast performance is expressed as an equivalent major principal stress reduction. It is shown that with the base panel geometry, the destressing program offers the same ERR reduction as a 9.6 MPa reduction in the far-field stress for the most critical stopes. Finally, the Copper Cliff Mine (CCM) panel destressing program is presented as a case study. The ore at risk and ERR are calculated over the extraction and destressing sequence in the pillar with a pillar-wide numerical model.

Experimental study of an innovative perforated air diffuser at real scale conditions

The European regulations are demanding more than ever to reduce the energy consumption for buildings and at the same time to raise the Indoor Environmental Quality to a higher standard. This challenge implies that the occupants inside the building should benefit from at least the same thermal comfort conditions at a lower energetical cost. The purpose of this research is to improve the performance of the air diffusers ventilation devices with the purpose of obtaining a more efficient mixing of the airflow from the air diffuser towards the ambient air. In this regard, an innovative cross shaped orifices perforated panel is analysed and compared to a regular panel with circular orifices. The experimental approach was carried out in a climatic chamber. The indoor thermal comfort was assessed at the same time by means of two different experimental devices, namely a thermal manikin and Comfort Sense equipment. The equivalent temperature was assess using the thermal manikin. The panels were also evaluated from the noise levels and pressure losses points of view. By evaluating the PMV and PPD thermal comfort indexes, the results highlighted a more comfortable ambience for a specific person in the room for the cross shaped lobed perforated panel in comparison to the circular shaped perforated panel. Furthermore, it seems that the special geometry of the lobed perforated panel does not generate supplementary noise. The pressure losses of the airflow through the perforated panels were reduced as well.

Higher-order finite element solution of graphene platelets reinforced nanocomposite curved panels with uniform/non-uniform porosity

This paper reveals the deformation behavior of graphene platelets reinforced (GPLR) nanocomposite shell panels including the porosity effects. The graphene platelets are assumed to be uniformly distributed across the thickness of the panel. The spatial-dependent elastic properties of the nanocomposite are computed via the modified Halpin-Tsai micromechanics scheme including the porosity effect. Three different patterns of porosity distribution are assumed through the thickness of the panel structure, namely, uniformly distributed (UD), non-uniformly distributed (ND-Type A), and non-uniformly distributed (ND-Type B). The kinematics of the present shallow shell structure is based on the equivalent single-layer higher-order theory via Green-Lagrange geometric nonlinearity. The weak form is governed through the principle of virtual work and further solved using 2D-isoparametric finite element approximations in conjunction with Picard’s successive iteration scheme. The convergence of the present model is achieved by performing a mesh refinement process and the accuracy of the model is verified by comparing numerical results with previously published literature. Finally, the influence of porosity distribution is analyzed on the center deflection of GPLR nanocomposite curved panels subjected to uniform and sinusoidal loads of different panel geometry under different support conditions.

Thick panel origami for load-bearing deployable structures

Origami-based deployable structures are of great interest as they can be manufactured and folded from thin flat sheets of material. However, the thin nature of origami panels results in a weak structural form at configurations close to unfolded or developed geometries. It, therefore, limits the functionality of such structures in applications involving load-bearing and full-unfolding. In this work, we show that by using the thick panel versions of the origami structures, one could obtain better load-bearing characteristics, especially at configurations close to the fully-unfolded geometries obtained through deployment. Specifically, we compare and contrast the geometry and structural behavior of a Yoshimura origami structure made from thin and thick panels. We present and implement a geometric framework to calculate the nodal coordinates of tessellated thick Yoshimura structures with arbitrarily specified panel dimensions and folded states. We discuss the structural modeling of a three-cell Yoshimura at a meter length scale and perform structural analysis at various folded configurations. We demonstrate the suitability of the thick panel structure over the thin panel version for resisting applied loads at configurations close to the fully-deployed state. The results indicate that employing thick panel geometries could enable the use of origami-based deployable structures at large length scales, especially for applications involving load-bearing.

Capacity model of CLT walls with openings and timber plasticization

This paper investigates the effect of timber plasticization on the ultimate lateral capacity of rocking Cross-Laminated Timber shear walls with different characteristics. Simplified capacity models predict a CLT wall ultimate capacity by multiplying the hold-down ultimate resistance by its distance to an assumed pivot point, often coincident with the panel edge. However, timber plasticization at the interface with the foundation can significantly reduce the lever arm of the hold down reaction. This paper aims at assessing the effect of timber plasticization and panel characteristics (geometry, width, presence of openings, etc.) on the position of the pivot point, expressed by the dimensionless lever arm τ, namely the ratio between the distance of the hold-down geometrical axis from the compressed timber resultant and the distance between the hold-down geometrical axis and the panel edge. An extended covariance-based sensitivity analysis of several Finite Element (FE) models, representing all the CLT shear wall design variability was carried out. The FE model, developed in Abaqus, has been calibrated on the experimental cyclic response of a CLT wall panel. Among the chosen parameters, the sensitivity analysis proved that the most significant ones affecting τ are two: the ratio between the hold-down reaction and the maximum resistance of the compressed timber, and the width of the opening. Accordingly, the authors estimated an elementary empirical regression equation based on the FE model results for predicting the dimensionless lever arm (τ) in the capacity equation of CLT panels. The use of this elementary formulation allows the designer to estimate with considerable accuracy the lateral capacity of a CLT panel given the panel geometry, the ultimate resistance of the hold-down, the compression strength of timber perpendicular to the grain and the vertical load. Almost all points used for the linear regression fall within the confidence bounds, thus proving the accuracy of the proposed empirical formula for the dimensionless lever arm.

Additive manufacturing on the façade: functional use of direct metal laser sintering hatch distance process parameters in building envelope

PurposeThe purpose of this article is on the functional usability of metal additive manufacturing (AM) direct metal laser sintering (DMLS) production technology process parameters in the construction industry. In the study, the advantages of thermal optimization and weight reduction in the case of the use of foam metals obtained by changing the hatch distance the production process parameter, in the production of facade panels in the architectural field are revealed.Design/methodology/approachThe methods in the study; production of the small scaled facade panels with nine different hatch distance parameters, determination of the thermal change with the infrared thermography method, microstructure examination, weight measurement.FindingsThe paper lays the groundwork for the manufacturability of lighter and lower thermal conductivity facade panels by changing the hatch distance parameters. Within the scope of the study, the definition of semi-open-cell foam aluminum and the product screening strategy offers innovation. Within the scope of the study, this scope is shared as an algorithmic summary. In addition, the study offers a new perspective within the scope of multiple optimizable panel production in facade panels with AM technology.Originality/valueHatch distance parameter change was first discussed in this study in the architectural field, and a semi-open cell foam aluminum panel was obtained with the scanning strategy determined within the scope of the study. This panel geometry, which is defined as semi-open cell foam aluminum, can be used as a design element by painting or coating the outer surface, it can be stated that it will also provide thermal and weight optimization.

Experimental investigation of automotive component in hybrid fibre reinforced thermoplastic design

A tailored use of continuous fibre reinforced plastics enables application in high volume car body structures. The combination of pultruded, load carrying, unidirectional, continuous fibre reinforced thermoplastic (FRTP) profiles and injection moulds, named “skeleton design”, is a promising approach to meet structural requirements and economical needs. This design offers the advantages of FRTP such as short cycle times of approx. 75 s and functional integration via injection moulding. A pre-serial BMW iX geometry of a windshield panel is used to analyse the impact of different fibre configurations in the profiles on the mechanical properties of the part. Therefore, different pultruded profiles with a cross-section of 10 mm x 10 mm made of polyamide 6 (PA6) with carbon fibres (CF) and glass fibres (GF) as well as a CF/GF hybrid were used. Furthermore, an optimized part using different materials within one part was investigated. Therefore, quasi-static and dynamic compression tests were performed on part level. It could be shown that the optimized parts meet mechanical requirements while decreasing material costs significantly.

Design charts for the local buckling analysis of integrally web-stiffened panels with filleted junctions subjected to uniaxial compressive loads

In this work, parametric finite element models are used to generate new design charts that provide the local buckling coefficient (ksl) of integrally web-stiffened panels (ISPs) subjected to uniaxial compressive loads, including the fillet radius effect. The numerical results from linear buckling analyses of hundreds of different panel geometries are presented in terms of four non-dimensional parameters: tw/ts, bw/bs, ts/bs and R/bwf, whereby the latter represents the effect of the fillet radius on ksl. An extensive survey based on ISPs geometries used in different types of aircraft wings was conducted to define the ranges of these four ratios. Within each range, discrete values of the four ratios were chosen and randomly combined to enable the construction of the finite element models used to obtain the new ksl curves. The proposed finite element modeling was validated by comparing the results with numerical and experimental results from the literature, showing a good agreement. Compared to non-filleted ISPs results, it is shown that the local buckling stresses of filleted ISPs may be significantly increased, allowing designers to optimize different ISPs geometries.

Optimal design of mass timber panels as dynamic insulation: simulations of steady and transient heat exchange

Mass timber panels could be designed as heat exchangers for use in building envelopes. Fresh air, drawn through geometrically optimized channels in the panel, is pre-tempered with building heat that would otherwise be lost to the exterior via conduction. Recent experiments have shown that timber heat exchanging panels can approach U ~0.1 W/m2K – but there are potential limitations. The sizing correlations which predict panel geometry and steady heat exchange must be numerically calibrated for building-scale contexts, the heat-exchange efficiency must be verified virtually, and practical thresholds for transient response time must be determined. This study uses numerical simulations to investigate these factors for one design ‘case’ of timber panels, and establishes a methodology for studies of further cases.

Experimental and analytical investigation on shear behavior of profiled steel sheet dry board composite wall system

Profiled steel sheet dry board (PSSDB) composite wall/panel system with advantages (like lightweight, enhanced flexibility, low-cost, simple pre-fabrication/erection process, no temporary formwork requirement etc.) is an innovative construction technology that has significant potential to be used as a viable alternative to its conventional counterparts in earthquake prone region. No significant research study is available on the structural behavior of PSSDB composite walls under in-plane shear loading. Nineteen PSSDB panels consisted of single profiled steel sheet (PSS) assembled with single or double plywood dry board (DB) are tested under shear loading to failure. The effects of boundary frame, central opening, concrete in-fill, fastener orientation, and panel geometry on load-deformation response, strength and failure modes are investigated and compared. Analytical models for shear capacities of PSSDB composite system of various configurations are developed based on modified code-based/existing equations and their performance validated using experimental results. These analytical models can be used by engineers in designing PSSDB composite system for practical construction.

Dynamic punching shear of impacting RC flat slabs with drop panels

Reinforced concrete flat slabs (FS) are sensitive to punching shear failure. Such failure may progress to the slab loss of supports and its downwards motion that is followed by its impact with the slab underneath. This slabs impact may initiate a progressive collapse of the entire building. The design guidelines provided by modern standards to avoid punching shear failure and to prevent post-punching loss of slab support in an attempt to prevent progressive collapse are based on static loads considerations and tests and do not include considerations and guidelines that are needed to guarantee resistance to impact loading. In our studies on the impact response of impacting slabs we learnt that increasing the slab thickness and the amount of reinforcement do not improve the slabs resistance to impact and cannot prevent the severe resulting damage. Drop panels are a common means to enhance the static resistance of slabs against punching shear as they increase the slab thickness around the column, where highest shear stresses are developed. The present paper aims at the investigation of the impact response of flat slabs with drop panels and examine their added contribution to reduce the post-impact damage and achieve a stable state of the impacted slab, thus preventing a following progressive collapse scenario. In addition to the local slab depth increase, the drop panel also limits the contact zone of the impacting slabs. Both aspects positively contribute to reducing the impact induced damage. The drop panel provides a means to locally increase the slab resistance without considerably increasing its mass, thus controlling the impact load intensity while increasing the slab’s resistance. The paper investigates the impacts of different possible combinations of two adjacent slabs with/without drop panels and finds that while flat slabs without drop panels fail upon impact, slabs with drop panels may survive the impact and avoid the following progressive collapse scenario. Opposed to static design where a drop panel contributes to the shear resistance, it was found that in the case of impact loading a large size drop panel increases the mass of the impacting slabs and may adversely affect the impact results, whereas a small size drop panel may not provide the required thickened zone. Examination of different drop panel geometries indicates that optimal drop panel dimensions exist which provide a stable final state which is associated with the minimum damage and a minimum permanent deflection. At larger or smaller drop panels the damage is larger and failure may occur. These are important findings that may help to improve the safe design of RC flat slabs.

Nonlinear modelling of the seismic response of masonry structures: Calibration strategies

In this paper, a simple and practitioners-friendly calibration strategy to consistently link target panel-scale mechanical properties (that can be found in national standards) to model material-scale mechanical properties is presented. Simple masonry panel geometries, with various boundary conditions, are utilized to test numerical models and calibrate their mechanical properties. The calibration is successfully conducted through five different numerical models (most of them available in commercial software packages) suitable for nonlinear modelling of masonry structures, using nonlinear static analyses. Firstly, the panel stiffness calibration is performed, focusing the attention to the shear stiffness. Secondly, the panel strength calibration is conducted for several axial load ratios by attempts using as reference the target panel strength deduced by well-known analytical strength criteria. The results in terms of panel strength for the five different models show that this calibration strategy appears effective in obtaining model properties coherent with Italian National Standard and Eurocode. Open issues remain for the calibration of the post-peak response of masonry panels, which still appears highly conventional in the standards.